Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published July 10, 2005 | Accepted Version + Published
Journal Article Open

Near-Infrared Surface Properties of the Two Intrinsically Brightest Minor Planets: (90377) Sedna and (90482) Orcus


We present low-resolution K-band spectra taken at the Gemini 8 m telescope of (90377) Sedna and (90482) Orcus (provisional designations 2003 VB_(12) and 2004 DW, respectively), currently the two minor planets with the greatest absolute magnitudes (i.e., the two most reflective minor planets). We place crude limits on the surface composition of these two bodies using a Hapke model for a wide variety of assumed albedos. The unusual minor planet Sedna was discovered on UT 2003 November 14 at roughly 90 AU, with 1.6 times the heliocentric and perihelion distances of any other bound minor planet. It is the first solar system object discovered between the Kuiper Belt and the Oort Cloud and may represent a transition population between the two. The reflectance spectrum of Sedna appears largely featureless at the current signal-to-noise ratio, suggesting a surface likely to be highly processed by cosmic rays. For large-grain models (100 μm to 1 cm) we find that Sedna cannot have more than 70% surface coverage of water ice and cannot have more than 60% surface coverage of methane ice, to 3 σ confidence. Minor planet Orcus shows strong water ice absorption corresponding to less than a 50% surface fraction for grain models 25 μm and larger. Orcus cannot have more than 30% of its surface covered by large (100 mm to 1 cm) methane grains, to 3 σ confidence.

Additional Information

© 2005 American Astronomical Society. Received 2004 March 26; accepted 2005 March 16. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina). We thank C. M. Mountain for granting Director's Discretionary time for this project under Gemini program IDs GN-2003BDD-3 and GN-2004A-DD-4. Alan Hatakeyama's support at the telescope was greatly appreciated. Operations at the telescope were greatly aided with the help of Simon Chan. Joe Jensen provided helpful input into constructing the observation sequence.

Attached Files

Published - 0004-637X_627_2_1057.pdf

Accepted Version - 0504280.pdf


Files (1.6 MB)
Name Size Download all
826.7 kB Preview Download
788.6 kB Preview Download

Additional details

August 22, 2023
October 19, 2023